To convey a conveyed material stably in such a manner that the material disposed between two rollers is under a predetermined tension, a roller-to-roller conveyance control apparatus includes speed controllers that each control the rotational speed of a corresponding roller, and provides speed references corresponding to the line speed to the speed controllers. At the same time, a tension detector detects the tension of the conveyed material between the two rollers, and a tension controller, which performs PI (Proportional-Integral) control or PID (Proportional-Integral-Derivative) control such that the tension of the conveyed material agrees with a command value, calculates a compensation value and outputs a tension control correction command to the tension control shaft, which is one of the shafts of the two rollers, as an addition to the speed reference described above.
Here, it is necessary to set the PI control gain for the tension controller appropriately in order for such a roller-to-roller conveyance control apparatus to convey a conveyed material stably. While the roller-to-roller conveyance control apparatus performs roller-to-roller conveyance, an operator checks the change in control gain and the corresponding tension response to adjust the control gain on a trial-and-error basis.
Common types of roller-to-roller conveyance control apparatus often cannot even convey a conveyed material with the desired conveying conditions unless the control gain for the tension controller is set to an appropriate value. Hence, in the initial adjustment stage, it is necessary to check the response of the detected tension value under operating conditions different from those of a normal operation, such as gentle acceleration/deceleration and a low speed, to make an adjustment to obtain a control gain with which stable conveyance can be achieved. It is then further necessary to repeat an operation of checking the response of the detected tension value under operating conditions closer to those of the normal operation to adjust the control gain such that the tension is further stabilized. This means that, because the adjustment of the control gain for a tension controller in a roller-to-roller conveyance control apparatus requires repeated changing of both operating conditions and control gains on a trial-and-error basis, it takes a significantly long time and much effort.
A solution to the problem described above is a technique disclosed in Patent Literature 1 that includes a model identification unit and identifies a control target model of a tension control system; the technique then uses the control target model in the repetition of a simulation and evaluation of the response when the control gain is changed to a candidate value in order to search for an optimal value of the control gain using a genetic algorithm and thereby automatically adjust the control gain of a tension control calculation unit.